We know where you’ve been: privacy, congestion tracking, and the future

With congestion a growing problem, many metropolitan areas are introducing …

Highway congestion is a serious problem that will only get worse as the US population grows. And our traditional solution to congestion—building more lanes—seems to be running out of steam. With governments facing record deficits, elected officials are having enough trouble finding the money to maintain existing infrastructure, to say nothing of adding new capacity. And in many places, proposals to expand highways encounter fierce resistance from nearby residents.

So public officials are searching for strategies to use existing highway capacity more efficiently. Recently they've begun experimenting with a new strategy for controlling congestion: demand-based pricing of scarce road capacity. Congestion pricing promises to kill two pigs with one bird, keeping traffic flowing smoothly while simultaneously generating new revenue that can be used for public investments. New technologies—notably RFID transponders and license-plate-reading cameras—are allowing the replacement of traditional tollbooths with cashless tolling at freeway speeds.

The congestion tolling projects that have been undertaken to date are relatively modest, but some transportation experts view them as a first step toward a future where tolls are collected on most major roads, and perhaps even the minor ones. Such schemes might abolish traffic jams once and for all, but they also have significant downsides. Ubiquitous tolling requires ubiquitous surveillance, which raises obvious civil liberties concerns. And more ambitious tolling schemes have proven broadly unpopular with voters, who believe they have already paid for the roads via other taxes.

In this article we'll consider whether congestion pricing can cure what ails the American transportation system. The economic arguments are compelling, and the current generation of tolled express lanes have produced real benefits. But we remain skeptical that the economic advantages of more ambitious tolling regimes are large enough to justify the potential costs in individual liberty. At a minimum, there needs to be much stronger legal and technological safeguards to ensure that infrastructure built to catch people evading tolls isn't used as a general-purpose system for governments to monitor and control motorists' every move.

Paying with money instead of time

The economic argument for congestion tolling is straightforward. During peak periods, space on a highway is a scarce resource. In our market-based economy, we allocate most scarce resources, from gasoline to ice cream, using prices. When demand outstrips supply, prices rise to bring them back into balance. Anyone who has stood in a long line for a "free" Ben and Jerry's ice cream cone knows that when a good is priced too cheaply, consumers effectively pay for it in time rather than money.

When Ben and Jerry's goes back to charging its regular prices for ice cream, the lines disappear. The same principle works on a congested freeway. Unlike traditional tolling regimes that charge motorists the same rate around the clock, congestion toll rates vary throughout the day to reflect changes in demand. The price will typically be highest during the morning and evening rush hours, and will be at its lowest late at night when most people are off the roads.

Ars Technica talked to Bob Poole, a transportation policy expert at the Reason Foundation, who pointed out that not all rush-hour drivers are commuters. Variable toll rates give non-commuters a stronger incentive to shift their trips to non-peak times. Tolls also encourage rush-hour drivers who are commuting to carpool or use public transit. And of course congestion tolls generate revenues that can be invested in new transportation infrastructure. That could mean widening existing freeways, building new ones, or expanding public transportation—all of which help reduce congestion.

Critics charge that congestion pricing amounts to a regressive tax, but Robert Puentes, a transportation scholar at the Brookings Institution, disagrees. He argued that even drivers of modest means benefit from the option to purchase access to a congestion-free traffic lane. He pointed to the example of a parent driving to pick up her child from a day-care service that charges a per-minute late fee. "It's a trade-off," Puentes said. "Folks generally appreciate having options for how they travel."

It's also worth remembering that the poorest commuters often cannot afford to drive at all. Not only would they benefit from more money being invested in public transportation, but they would also directly benefit from shorter bus rides on congestion-free toll lanes.

The phantom tollbooth

A new generation of cashless tolling systems eliminates these problems and allows motorists to enter and leave tolled roads at full speed.

Congestion tolling has been widely discussed in traffic planning circles since at least the 1960s. However, adoption has been slow. Until recently, two major obstacles have stood in the way.

One obstacle was technology. If you live in a part of the United States that has traditional toll roads, the idea that tolling could reduce congestion probably sounds crazy. Driving up Interstate 95 from Washington to New York, for example, you'll waste a significant amount of time waiting in lines at various toll plazas. A system of electronic transponders called EZ-Passes, introduced in the 1990s, has reduced congestion at toll plazas but hasn't eliminated it. EZ-Pass lanes are usually modified toll lanes that are too narrow for cars to safely go through at highway speeds. And when the roads get busy, EZ-Pass users get stuck in line behind users paying cash.

A new generation of cashless tolling systems eliminates these problems and allows motorists to enter and leave tolled roads at full speed. Peter Samuel, the editor of TOLLROADSnews, told Ars that cashless tolling has been made possible by a combination of two technologies. One is RFID-based transponders. The first generation of transponders, such as the EZ-Pass, were battery-powered active transponders. Newer RFID tolling systems are based on passive transponders. They're smaller, cheaper, and have no battery to replace.

In the long run, these transponders may be supplanted by emerging Dedicated Short-Run Communications (DSRC) standards. In 2003, the FCC set aside spectrum in the 5.9 GHz range for dedicated vehicle-to-vehicle and vehicle-to-infrastructure communications. Designers envision DSRC being used for a number of purposes, including tolling. Presumably, vehicles' built-in DSRC hardware will be significantly more powerful than an RFID transponder, opening the door to sophisticated cryptographic schemes that could minimize information leakage.

The second key technology for cashless tolling is automated license plate readers. Samuel said this technology has its origins in the United Kingdom in the 1990s, where the government built an extensive network of surveillance cameras with license-plate-reading technology as a way to fight car bombings by the Irish Republican Army. The network proved useful a decade later when London introduced a congestion charge (now £10) for entry into central London. The cameras snap pictures of all vehicles entering and leaving the congestion zone and match their license plates against government records.

Samuel told Ars that the technology for recognizing license plates has steadily improved, and it is now widely used in American tolling systems. The most common arrangement is a hybrid approach, in which most vehicles are identified using RFID transponders, and license-plate cameras are used as a backstop to identify vehicles that lack transponders.

Timothy B. Lee / Timothy covers tech policy for Ars, with a particular focus on patent and copyright law, privacy, free speech, and open government. His writing has appeared in Slate, Reason, Wired, and the New York Times.